This invention relates to synchronizing arrangements for generating synchronizing and blanking signals, which arrangement is readily adaptable for various television standards.
There are four main television standards in use throughout the world; NTSC, SECAM, PAL and PAL-M. Making receivers for each one of these various standards poses no problem, since there is sufficient manufacturing volume to economically justify this specialization.
Studio apparatus using sync generators, such as for example cameras, is however, a different situation. It is difficult to justify making a sync generator for just one standard due to the low volume involved. One solution is shown in U.S. Pat. No. 4,169,659, which shows a sync generator that is adaptable to different standards. However, a cost penalty is then incurred on every unit because each unit must include portions applicable only to other standards, even though they may never be used. Further, once built, the adaptable unit cannot be readily changed to produce different pulses as may be required, e.g., a pulse occurring at the 19th horizontal line to control insertion of a vertical interval test signal when the unit was designed to produce a pulse on the 21st horizontal line. Another problem is that the circuit cannot be changed without complete redesign of hardware to generate a new standard as this may become necessary. For example, one standard that is sometimes used has 24 frames per second to match that of film, and 655 lines per frame, which standard has the same bandwidth as that of NTSC.
It is therefore desirable to have a sync generator that is readily adaptable in the field among both present and future standards. It is also desirable that there be only a small cost penalty for this adaptability, which then is offset by the larger volume of manufacture of the adaptable circuit.